US20080157630A1 - Piezoelectric vibrating piece and piezoelectric vibrating device - Google Patents
Piezoelectric vibrating piece and piezoelectric vibrating device Download PDFInfo
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- US20080157630A1 US20080157630A1 US11/956,254 US95625407A US2008157630A1 US 20080157630 A1 US20080157630 A1 US 20080157630A1 US 95625407 A US95625407 A US 95625407A US 2008157630 A1 US2008157630 A1 US 2008157630A1
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- United States
- Prior art keywords
- piezoelectric vibrating
- vibrating piece
- electrode
- electrode film
- film
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- 239000010931 gold Substances 0.000 claims description 19
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 18
- 229910052737 gold Inorganic materials 0.000 claims description 18
- 229910052782 aluminium Inorganic materials 0.000 claims description 12
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 12
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 11
- 239000010949 copper Substances 0.000 claims description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- 229910052802 copper Inorganic materials 0.000 claims description 6
- 239000010936 titanium Substances 0.000 claims description 6
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 5
- 229910052721 tungsten Inorganic materials 0.000 claims description 5
- 239000010937 tungsten Substances 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 3
- MOWMLACGTDMJRV-UHFFFAOYSA-N nickel tungsten Chemical compound [Ni].[W] MOWMLACGTDMJRV-UHFFFAOYSA-N 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 2
- 239000010408 film Substances 0.000 description 38
- 239000013078 crystal Substances 0.000 description 27
- 238000010438 heat treatment Methods 0.000 description 16
- 239000000853 adhesive Substances 0.000 description 8
- 230000001070 adhesive effect Effects 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 7
- 229910052709 silver Inorganic materials 0.000 description 7
- 239000004332 silver Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 239000010453 quartz Substances 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 4
- 230000002950 deficient Effects 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- 239000004593 Epoxy Substances 0.000 description 3
- 238000001465 metallisation Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910000679 solder Inorganic materials 0.000 description 3
- 238000004544 sputter deposition Methods 0.000 description 3
- 238000000605 extraction Methods 0.000 description 2
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 230000002123 temporal effect Effects 0.000 description 2
- 229920001187 thermosetting polymer Polymers 0.000 description 2
- 238000004891 communication Methods 0.000 description 1
- 239000011231 conductive filler Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 229910000833 kovar Inorganic materials 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/05—Holders; Supports
- H03H9/0538—Constructional combinations of supports or holders with electromechanical or other electronic elements
- H03H9/0547—Constructional combinations of supports or holders with electromechanical or other electronic elements consisting of a vertical arrangement
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/05—Holders; Supports
- H03H9/10—Mounting in enclosures
- H03H9/1007—Mounting in enclosures for bulk acoustic wave [BAW] devices
- H03H9/1014—Mounting in enclosures for bulk acoustic wave [BAW] devices the enclosure being defined by a frame built on a substrate and a cap, the frame having no mechanical contact with the BAW device
- H03H9/1021—Mounting in enclosures for bulk acoustic wave [BAW] devices the enclosure being defined by a frame built on a substrate and a cap, the frame having no mechanical contact with the BAW device the BAW device being of the cantilever type
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/13—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials
- H03H9/132—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials characterized by a particular shape
Definitions
- piezoelectric vibrating devices such as crystal oscillators or crystal controlled oscillators need to be downsized.
- a crystal vibrating piece using piezoelectric vibrating devices is attached to a ceramic package by thermosetting resin.
- the thermosetting resin is heated up either 150° C. or 250° C. to attach the crystal vibrating piece. Therefore, the crystal vibrating piece is heated up either 150° C. or 250° C. as well.
- the piezoelectric vibrating device is treated with heat by a solder reflow furnace and the crystal vibrating piece in the package is also heated up to 200° C.
- the first surface on the first surface, it has a first electrode film having a bigger coefficient of thermal expansion than the piezoelectric piece, and on the second surface, a second electrode film having a smaller coefficient of thermal expansion than the piezoelectric piece.
- the piezoelectric piece is excited by those first and second electrode films.
- the coefficient of thermal expansion of first electrode film is bigger than of the piezoelectric piece so that it has a factor to drift to the lower frequency.
- the coefficient of thermal expansion of second electrode film is smaller than of the piezoelectric piece so that it has a factor to drift to the higher frequency. Therefore, even though the piezoelectric piece which is after having a treated with heat, the first electrode film and the second electrode film work to negate frequency changes each other. Thus, the frequency change is smaller after the heat treatment.
- the piezoelectric electrode piece of a second aspect is that the first electrode film is formed by a first thickness and the second electrode film is formed by a second thickness which is designated ratio to the first thickness.
- the piezoelectric vibrating piece of a third aspect is that the first and second electrode films are symmetric shape across a piezoelectric piece and have the same dimensions.
- the piezoelectric piece is excited by the first and the second electrode films. Because they are symmetric shape and have same dimension across a piezoelectric vibrating device, they can negate the influence of frequency change each other.
- the piezoelectric vibrating piece of a forth aspect is the first electrode film is formed in between the electrode piece through a third electrode film.
- the third electrode film when the first electrode film cannot be deposited, can be formed as a substrate of double layer and the first electrode film can be formed on it.
- the piezoelectric vibrating piece of a fifth aspect is that the first electrode film is a gold film and the second electrode film is an aluminum film.
- the piezoelectric vibrating device of other aspects have a package having the piezoelectric vibrating piece of the first or fifth aspect and a cover making a vacuum state and sealing package.
- a piezoelectric device by using a productive and high quality piezoelectric vibrating piece, a piezoelectric device can be manufactured.
- a piezoelectric vibrating piece and piezoelectric device which has low frequency change to temperature change at a heat treatment can be provided.
- the first and second electrode films are essential, and the electrode films themselves can prevent frequency change at the heat treatment. Therefore, a frequency change can be prevented within a defined value despite of the temperature elevation without increasing of number of parts.
- FIGS. 1 ( a ) and ( b ) illustrate an embodiment of the piezoelectric vibrating piece 50 .
- FIG. 2 ( a ) is a perspective view showing a whole format of rectangle-shape piezoelectric vibrating piece 20 and ( b ) is a cross-sectional view taken form line B-B of the rectangular-shaped piezoelectric vibrating piece 20 .
- FIG. 3 ( a ) illustrates a piezoelectric vibration piece of a disc geometry and (b) a hexagonal geometry.
- the FIG. 4 is a graph, which has frequency change in vertical scale and time in a horizontal scale, showing a temporal change of frequency change by a heat treatment of the piezoelectric vibrating piece
- FIG. 5 ( a ) illustrates a crystal oscillator and ( b ) illustrates a cylinder type oscillator.
- the package 51 comprises a base 51 a , a wall 51 b and a floor 51 c as shown in FIG. 1( b ).
- An internal space of package 51 is formed by covering with the wall 51 b , and the piezoelectric vibrating piece 20 is stored in the internal space.
- the floor 51 c is arranged on the base 51 a to support the piezoelectric vibrating piece 20 with a designated height.
- an electrode 52 is formed comprised of a nickel plate or gold plate on tungsten metallization.
- An electrode 52 is connected to a mounting terminal 55 formed under the base 51 a . Because of this, a driving voltage can be transmitted to the electrode 52 through the mounting terminal 55 and provided to the piezoelectric vibrating piece 20 .
- the mounting terminal 55 and the electrode 52 can be formed by leading the exterior of package 51 with metallization, or by using a conductive through hole formed by tungsten metallization before firing of the base 51 a.
- the upper end of wall 51 b is sealed by a cover 59 fixed by a seal 58 .
- the cover 59 is preferably formed by a ceramic comprising kneading material of an aluminum oxide. If it is formed by metal members, such as kovar, the cover 59 is fixed by a method of welding to the wall 51 b.
- the piezoelectric vibrating piece 20 is, for example, formed with a crystal having a rectangular or round shape.
- the rectangular shaped piezoelectric vibrating piece 20 shown in FIG. 1 and has a first electrode 23 formed on a first surface with a rectangular shape, and a second electrode 25 formed on a second surface with a rectangular shape.
- the quadrate piezoelectric vibrating piece 20 is, for example, a very small vibrating piece which vibrates at 100 MHz and its size is about 2.0 mm long and 2.0 mm wide.
- a first electrode pattern 23 is formed on a substrate third electrode pattern 27 .
- a second electrode pattern 25 is formed on the rear surface of the piezoelectric vibrating piece 20 . Both the first electrode pattern 23 and the second electrode pattern 25 are formed at the central area of the piezoelectric vibrating piece 20 and have a first extraction electrode 23 - a and a second extraction electrode 25 - a extracting form the central area to the edge.
- the third electrode pattern 27 is a chrome layer of approximately 50 angstrom ⁇ 300 angstrom. In order to be uninfluential to a thermal expansion of a gold (Au) layer, the third electrode pattern 27 is preferably thinner than the gold layer.
- the first electrode pattern 23 is, for example, a gold layer of approximately 100 angstrom to 3000 angstrom. The gold layer cannot be evaporated onto a piezoelectric material, such as crystal. For that reason, the chrome layer is formed as a substrate. Total thickness of an electrode pattern of the first electrode pattern 23 and the third electrode pattern 27 is approximately 150 to 3300 angstrom.
- the device forms the metal thin film one by one on each side of the piezoelectric vibrating device, one deposition device forms an aluminum layer and the other device forms the gold layer.
- the first electrode pattern 23 and the second electrode pattern 25 can work with each other to negate the frequency change.
- the heat treatment the piezoelectric vibrating piece 20 receives is a heat treatment which occurs when the piezoelectric vibrating piece 20 is mounted to the package 51 by the electrically conductive adhesive 57 , or a heat treatment which occurs when the piezoelectric vibrating device 50 is mounted or reflowed.
- the coefficient of thermal expansion of gold is smaller than a single quartz crystal, and of aluminum is bigger than a single quartz crystal.
- the coefficient of thermal expansion of crystal at 227° C. (550K) is 11.4 ⁇ 10 ⁇ 6 for a vertical direction and 19.5 ⁇ 10 ⁇ 6 for a parallel direction.
- the coefficient of thermal expansion of gold is 15.4 ⁇ 10 ⁇ 6 and of aluminum is 26.4 ⁇ 10 ⁇ 6 at 227° C. (500K).
- silver instead of a gold layer of the first electrode pattern 23 , silver (Ag) can be used. And, the coefficient of thermal expansion of the silver is 19.0 ⁇ 10 ⁇ 6 and for a silver layer, it is formed with a silver layer of about 500 to 15000 angstrom. If the ratio of silver layer and aluminum layer is about 5:7, they negate their frequency changes of each other.
- a chrome layer of the third electrode pattern 27 as a substrate for a gold or silver layer
- a tungsten (W) layer, a nickel (Ni) layer, a nickel tungsten layer or a titanium (Ti) layer can be used.
- FIG. 4 is a graph having a frequency change in vertical scale and time in a horizontal scale, and shows a temporal change of frequency change by a heat treatment of the piezoelectric vibrating piece.
- the piezoelectric vibration pieces 20 , 31 and 35 are bonded by the hot cured electrically conductive adhesive 57 to a ceramic package, it is heated up to about 250° C.
- the piezoelectric vibrating device 50 is also treated with heat of about 250° C. when it is put into the reflow furnace.
- a frequency change should be under 81 which is the standard value of piezoelectric vibrating piece 50 , which is also called frequency stability, for example, under frequency ⁇ 10 ⁇ 4 .
- the frequency change of the piezoelectric vibrating device becomes greater.
- a frequency change 89 of piezoelectric vibrating device of existing product is over the standard value 81 of frequency change, and the value continues to be over after the heat treatment 83 .
- the frequency change 87 of the piezoelectric vibrating device 50 of this embodiment is basically not over the standard value of frequency change 81 .
- the crystal oscillator 40 a of FIG. 5( a ) has an integrated circuit 45 on the base 51 a on the lower side of the piezoelectric vibrating piece 20 of the piezoelectric vibrating device 50 described with respect to FIG. 1 . That is, in the crystal oscillator 40 a , when the piezoelectric vibrating piece 20 arranged inside vibrates, the vibration is inputted to the integrated circuit 45 and then it will work as an oscillator after designated frequency signal is removed.
- FIG. 5( b ) is a schematic view of cylinder type oscillator 40 b .
- the above-mentioned piezoelectric vibrating piece 20 is used for this cylinder type oscillator 40 b .
- the cylinder type oscillator 40 b has a metal cap to store the piezoelectric vibrating piece 20 inside.
- the cap 46 is pressed to a stem 47 and the inside is kept in a vacuum state.
- two leads 48 are allocated.
- the piezoelectric vibrating piece 20 is attached by the electrically conductive adhesive 57 to the leads 48 .
- the piezoelectric vibrating piece 20 is vibrated when it receives a certain current form an electrode.
- crystal vibrating piece is explained as one of examples of a piezoelectric vibrating piece; however, as a piezoelectric vibrating piece, lithium niobate or other piezoelectric single quartz besides crystal can be used.
Abstract
Description
- This application claims the benefit of Japanese Patent Application No. 2006-354725 filed on Dec. 28, 2006 in the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference.
- This application relates generally to the field of piezoelectric devices.
- With the miniaturization of various communication devices or electronic devices, piezoelectric vibrating devices such as crystal oscillators or crystal controlled oscillators need to be downsized. A crystal vibrating piece using piezoelectric vibrating devices is attached to a ceramic package by thermosetting resin. On this occasion, the thermosetting resin is heated up either 150° C. or 250° C. to attach the crystal vibrating piece. Therefore, the crystal vibrating piece is heated up either 150° C. or 250° C. as well. Also, when a packaged piezoelectric vibrating device is mounted to an epoxy laminate, the piezoelectric vibrating device is treated with heat by a solder reflow furnace and the crystal vibrating piece in the package is also heated up to 200° C.
- After the temperature of piezoelectric vibrating device became 200° C. through the heat treatment, the piezoelectric vibrating device is back to a room temperature. However, sometimes piezoelectric vibrating devices are not back to a designated primary frequency form a varied frequency. In such a case, those products are considered as defective products at the shipment. Supposedly, when such defective products of piezoelectric vibration devices are mounted to the epoxy laminate, they go through a heat treatment such as solder reflow furnace. Inside of the solder reflow furnace is set to 180° C. or 250° C. and after ten seconds, the piezoelectric vibrating device is treated with heat. As described above, after the piezoelectric vibrating device is treated with heat, its frequency is varied as well, even if it is back to a room temperature, and the whole epoxy laminate is considered as defective products. Japanese Unexamined Patent Application Publication No. 2003-17977 disclosed that although such piezoelectric vibrating device considered as a defective product, it is acknowledged that it vibrated proper frequency after few months because remaining stress of crystal vibrating piece was released.
- However, if it does not work properly for few months, the product cannot be shipped. Especially, when it is more than 100 MHz, it tends to have a greater frequency change.
- Therefore, the purpose of this invention is to provide a piezoelectric vibrating piece and piezoelectric vibrating device having less frequency change for a heat change a heat treatment.
- A piezoelectric vibrating piece of a first aspect having a first and a second surface at an opposing side of the first surface is comprised of an electrode piece having designated coefficient of thermal expansion, a first electrode film having bigger coefficient of thermal expansion than the designated coefficient of thermal expansion and formed on the first surface; and a second electrode film having smaller coefficient of thermal expansion than the designated coefficient of thermal expansion and formed on the second surface. For the vibrating piece, lithium niobate or other piezoelectric single crystal materials besides crystal can be used.
- According to the above-mentioned format, on the first surface, it has a first electrode film having a bigger coefficient of thermal expansion than the piezoelectric piece, and on the second surface, a second electrode film having a smaller coefficient of thermal expansion than the piezoelectric piece. The piezoelectric piece is excited by those first and second electrode films. At the condition that the first electrode film is treated with heat, the coefficient of thermal expansion of first electrode film is bigger than of the piezoelectric piece so that it has a factor to drift to the lower frequency. On the other hand, the coefficient of thermal expansion of second electrode film is smaller than of the piezoelectric piece so that it has a factor to drift to the higher frequency. Therefore, even though the piezoelectric piece which is after having a treated with heat, the first electrode film and the second electrode film work to negate frequency changes each other. Thus, the frequency change is smaller after the heat treatment.
- The piezoelectric electrode piece of a second aspect is that the first electrode film is formed by a first thickness and the second electrode film is formed by a second thickness which is designated ratio to the first thickness.
- To the coefficient of thermal expansion of crystal, the coefficient of thermal expansion of the first electrode film and of the second electrode film are not exactly symmetric. Because of this, in order to negate frequency change, adjust the thickness of electrode films of the first and second electrode films. The thickness of electrode film can be changed properly in the process of making a thin film by sputtering CVD by changing power output or fixing a film forming time.
- The piezoelectric vibrating piece of a third aspect is that the first and second electrode films are symmetric shape across a piezoelectric piece and have the same dimensions.
- According to the above-mentioned format, the piezoelectric piece is excited by the first and the second electrode films. Because they are symmetric shape and have same dimension across a piezoelectric vibrating device, they can negate the influence of frequency change each other.
- The piezoelectric vibrating piece of a forth aspect is the first electrode film is formed in between the electrode piece through a third electrode film.
- According to the above-mentioned format, when the first electrode film cannot be deposited, the third electrode film can be formed as a substrate of double layer and the first electrode film can be formed on it.
- The piezoelectric vibrating piece of a fifth aspect is that the first electrode film is a gold film and the second electrode film is an aluminum film.
- According to the above-mentioned format, by using a high conductive metal film, a fine electric characteristic piezoelectric vibrating piece with small CI value can be obtained.
- The piezoelectric vibrating device of other aspects have a package having the piezoelectric vibrating piece of the first or fifth aspect and a cover making a vacuum state and sealing package.
- According to the above-mentioned format, by using a productive and high quality piezoelectric vibrating piece, a piezoelectric device can be manufactured.
- According to this invention, a piezoelectric vibrating piece and piezoelectric device which has low frequency change to temperature change at a heat treatment can be provided. As a necessary excitation electrode to vibrate, the first and second electrode films are essential, and the electrode films themselves can prevent frequency change at the heat treatment. Therefore, a frequency change can be prevented within a defined value despite of the temperature elevation without increasing of number of parts.
- The embodiments of this invention are explained with following figures.
-
FIGS. 1 (a) and (b) illustrate an embodiment of the piezoelectric vibratingpiece 50. -
FIG. 2 (a) is a perspective view showing a whole format of rectangle-shape piezoelectric vibratingpiece 20 and (b) is a cross-sectional view taken form line B-B of the rectangular-shaped piezoelectric vibratingpiece 20. -
FIG. 3 (a) illustrates a piezoelectric vibration piece of a disc geometry and (b) a hexagonal geometry. - The
FIG. 4 is a graph, which has frequency change in vertical scale and time in a horizontal scale, showing a temporal change of frequency change by a heat treatment of the piezoelectric vibrating piece -
FIG. 5 (a) illustrates a crystal oscillator and (b) illustrates a cylinder type oscillator. -
FIG. 1 shows an embodiment of apiezoelectric vibrating device 50 of this invention.FIG. 1( a) is a top schematic view of thepiezoelectric vibrating device 50 andFIG. 1( b) is a cross-sectional view taken form line B-B ofFIG. 1( a). InFIG. 1 , the piezoelectricvibrating device 50 shows an example of a format of a rectangular shapedpiezoelectric vibrating piece 20 and thepiezoelectric vibrating device 50 stores thepiezoelectric vibrating piece 20 in apackage 51. Thepackage 51, for example, as an insulting material, is formed and sintered by laminating several ceramic green sheets comprising a kneaded aluminum oxide. - In this embodiment, the
package 51 comprises abase 51 a, awall 51 b and afloor 51 c as shown inFIG. 1( b). An internal space ofpackage 51 is formed by covering with thewall 51 b, and the piezoelectric vibratingpiece 20 is stored in the internal space. Then, thefloor 51 c is arranged on thebase 51 a to support the piezoelectric vibratingpiece 20 with a designated height. On thefloor 51 c, for example, anelectrode 52 is formed comprised of a nickel plate or gold plate on tungsten metallization. - An
electrode 52 is connected to amounting terminal 55 formed under thebase 51 a. Because of this, a driving voltage can be transmitted to theelectrode 52 through themounting terminal 55 and provided to thepiezoelectric vibrating piece 20. Specifically, as shown inFIG. 1( b), themounting terminal 55 and theelectrode 52 can be formed by leading the exterior ofpackage 51 with metallization, or by using a conductive through hole formed by tungsten metallization before firing of thebase 51 a. - An electrically
conductive adhesive 57 is coated on theelectrode 52 and a base portion 29 of the piezoelectric vibratingpiece 20 is connected. As the electrically conductive adhesive 57, for a synthetic resin as an adhesive ingredient exercising a bonding, conductive filler (including conductive particles of fine grain of silver) and designated solvent can be used. In order to solidify the electrically conductive adhesive 57, thewhole package 51 is heated in a furnace with a temperature set at approximately 150° C. to 250° C. to heat the electricallyconductive adhesive 57. - The upper end of
wall 51 b is sealed by acover 59 fixed by aseal 58. Thecover 59 is preferably formed by a ceramic comprising kneading material of an aluminum oxide. If it is formed by metal members, such as kovar, thecover 59 is fixed by a method of welding to thewall 51 b. - The piezoelectric vibrating
piece 20 is, for example, formed with a crystal having a rectangular or round shape. The rectangular shaped piezoelectric vibratingpiece 20 shown inFIG. 1 and has afirst electrode 23 formed on a first surface with a rectangular shape, and asecond electrode 25 formed on a second surface with a rectangular shape. -
FIG. 2( a) is a perspective view of the rectangular-shapedpiezoelectric vibrating piece 20, and (b) is a cross-sectional view taken form B-B of the rectangular-shapedpiezoelectric vibrating piece 20. A base material of the rectangular-shapedpiezoelectric vibrating piece 20 is almost quadrate and is formed with AT cut-processed crystal single quartz wafer 10. - Also, the quadrate piezoelectric vibrating
piece 20 is, for example, a very small vibrating piece which vibrates at 100 MHz and its size is about 2.0 mm long and 2.0 mm wide. On the surface of the rectangular-shapedpiezoelectric vibrating piece 20, afirst electrode pattern 23 is formed on a substratethird electrode pattern 27. On the rear surface of the piezoelectric vibratingpiece 20, asecond electrode pattern 25 is formed. Both thefirst electrode pattern 23 and thesecond electrode pattern 25 are formed at the central area of the piezoelectric vibratingpiece 20 and have a first extraction electrode 23-a and a second extraction electrode 25-a extracting form the central area to the edge. - The
third electrode pattern 27 is a chrome layer of approximately 50 angstrom˜300 angstrom. In order to be uninfluential to a thermal expansion of a gold (Au) layer, thethird electrode pattern 27 is preferably thinner than the gold layer. Thefirst electrode pattern 23 is, for example, a gold layer of approximately 100 angstrom to 3000 angstrom. The gold layer cannot be evaporated onto a piezoelectric material, such as crystal. For that reason, the chrome layer is formed as a substrate. Total thickness of an electrode pattern of thefirst electrode pattern 23 and thethird electrode pattern 27 is approximately 150 to 3300 angstrom. - On the other hand, the
second electrode pattern 25 is, for example, formed with an aluminum (Al) layer of approximately 700 to 21000 angstrom. That is, the ratio of the thickness of the gold layer of thefirst electrode pattern 23 and the aluminum layer of thesecond electrode pattern 25 is about 1:7. Also, thefirst electrode pattern 23 and thesecond electrode pattern 25 are preferably almost same electrode pattern shape and diameter. The thickness of electrode film can be changed properly in the process of making a thin film by sputtering or CVD by changing power output or fixing a film forming time. There is a device to form the same gold thin film on the both sides of a piezoelectric vibrating piece at once in the sputtering or CVD. If the device forms the metal thin film one by one on each side of the piezoelectric vibrating device, one deposition device forms an aluminum layer and the other device forms the gold layer. Using such a format, thefirst electrode pattern 23 and thesecond electrode pattern 25 can work with each other to negate the frequency change. - The heat treatment the piezoelectric vibrating
piece 20 receives is a heat treatment which occurs when the piezoelectric vibratingpiece 20 is mounted to thepackage 51 by the electrically conductive adhesive 57, or a heat treatment which occurs when the piezoelectric vibratingdevice 50 is mounted or reflowed. At such temperature of the heat treatment, the coefficient of thermal expansion of gold is smaller than a single quartz crystal, and of aluminum is bigger than a single quartz crystal. The coefficient of thermal expansion of crystal at 227° C. (550K) is 11.4×10−6 for a vertical direction and 19.5×10−6 for a parallel direction. Also, the coefficient of thermal expansion of gold is 15.4×10−6 and of aluminum is 26.4×10−6 at 227° C. (500K). - Instead of a gold layer of the
first electrode pattern 23, silver (Ag) can be used. And, the coefficient of thermal expansion of the silver is 19.0×10−6 and for a silver layer, it is formed with a silver layer of about 500 to 15000 angstrom. If the ratio of silver layer and aluminum layer is about 5:7, they negate their frequency changes of each other. - Instead of a gold layer of the
first electrode pattern 23, a copper (Cu) layer can also be used. The coefficient of thermal expansion of copper is 16.7×10−6. The copper layer can be deposited directly to a piezoelectric material such as crystal. In such a case, thethird electrode pattern 27 as a substrate is not needed. The copper layer and aluminum layer negate each other's frequency changes when the ratio of thickness is about 7:10. - Also, instead of a chrome layer of the
third electrode pattern 27 as a substrate for a gold or silver layer, a tungsten (W) layer, a nickel (Ni) layer, a nickel tungsten layer or a titanium (Ti) layer can be used. - When a crystal single quartz wafer 10 is AT cut, a basic vibrating frequency of the vibrating piece can be shown as about 1670/f (MHz)=t(μm). Therefore, the ratio of the above-mentioned
first electrode pattern 23 and thesecond electrode pattern 25 can be changed with consideration of a ratio of thefirst electrode pattern 23 and thesecond electrode pattern 25 properly to desired basic frequency. -
FIG. 3 is a plan view of showing other piezoelectric vibrating pieces, and (a) is apiezoelectric vibration piece 31 of disc geometry and (b) is a piezoelectric vibratingpiece 35 of hexagonal shape. Both of them have the same shape of electrode pattern and diameter of thefirst electrode pattern 23 and thesecond electrode pattern 25. The shape of electrode pattern is not necessarily the same shape of a piezoelectric piece. If forming thefirst electrode pattern 23 and thesecond electrode pattern 25 with the above-mentioned condition, thepiezoelectric vibration piece 31 of disc geometry or the hexagonalpiezoelectric vibration piece 35 which has less frequency change at the temperature change at heat treatment can be manufactured. Therefore, the piezoelectric vibration piece can be any of rectangle, round, or polygonal shape. -
FIG. 4 is a graph having a frequency change in vertical scale and time in a horizontal scale, and shows a temporal change of frequency change by a heat treatment of the piezoelectric vibrating piece. When thepiezoelectric vibration pieces device 50 is also treated with heat of about 250° C. when it is put into the reflow furnace. Even in such environments, a frequency change should be under 81 which is the standard value of piezoelectric vibratingpiece 50, which is also called frequency stability, for example, under frequency×10−4. - When the piezoelectric vibrating device is processed with a
heat treatment 83 in the reflow furnace of about 250° C. within the range that the arrows show in the figure starting untreated, the frequency change of the piezoelectric vibrating device becomes greater. Afrequency change 89 of piezoelectric vibrating device of existing product is over thestandard value 81 of frequency change, and the value continues to be over after theheat treatment 83. On the other hand, thefrequency change 87 of the piezoelectric vibratingdevice 50 of this embodiment is basically not over the standard value offrequency change 81. - A metal film having a bigger coefficient of thermal expansion than crystal has a factor that decreases the oscillating frequency. A metal film having a smaller coefficient of thermal expansion than crystal has a factor to change oscillating frequency to a higher position. Therefore, although after applying a
heat treatment 83, a metal film changing the oscillating frequency to a lower value is formed on one side and a metal film changing the oscillating frequency to a higher value is formed on the rear side, it is considered that the frequency change of the piezoelectric vibratingdevice 50 is not over thestandard value 81. It is also considered that if the piezoelectric vibratingdevice 50 is back to a room temperature, its frequency returns to a normal resonance frequency. -
FIG. 5( a) shows acrystal oscillator 40 a. Thecrystal oscillator 40 a has mostly the same format of the piezoelectric vibratingdevice 50 described with respect toFIG. 1 . Therefore, the format and function of the piezoelectric vibratingdevice 50 and the piezoelectric vibratingpiece 20 is omitted by numbering the same numbers to the figures. - The
crystal oscillator 40 a ofFIG. 5( a) has an integratedcircuit 45 on the base 51 a on the lower side of the piezoelectric vibratingpiece 20 of the piezoelectric vibratingdevice 50 described with respect toFIG. 1 . That is, in thecrystal oscillator 40 a, when the piezoelectric vibratingpiece 20 arranged inside vibrates, the vibration is inputted to theintegrated circuit 45 and then it will work as an oscillator after designated frequency signal is removed. -
FIG. 5( b) is a schematic view ofcylinder type oscillator 40 b. The above-mentionedpiezoelectric vibrating piece 20 is used for thiscylinder type oscillator 40 b. As theFIG. 5( b) shows, thecylinder type oscillator 40 b has a metal cap to store the piezoelectric vibratingpiece 20 inside. Thecap 46 is pressed to astem 47 and the inside is kept in a vacuum state. Also, in order to keep the piezoelectric vibratingpiece 20 stored in the cap 75, two leads 48 are allocated. The piezoelectric vibratingpiece 20 is attached by the electrically conductive adhesive 57 to the leads 48. The piezoelectric vibratingpiece 20 is vibrated when it receives a certain current form an electrode. - In the above, crystal vibrating piece is explained as one of examples of a piezoelectric vibrating piece; however, as a piezoelectric vibrating piece, lithium niobate or other piezoelectric single quartz besides crystal can be used.
Claims (20)
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US20100066213A1 (en) * | 2008-09-17 | 2010-03-18 | Nihon Dempa Kogyo Co., Ltd. | Method of manufacturing quartz resonator element, quartz resonator element, quartz resonator, and quartz oscillator |
US20110227457A1 (en) * | 2010-02-25 | 2011-09-22 | Nihon Dempa Kogyo Co., Ltd. | Piezoelectric vibrating pieces and devices, and methods for manufacturing same |
US20120091859A1 (en) * | 2010-10-13 | 2012-04-19 | Seiko Epson Corporation | Piezoelectric generator, sensor node, and method of manufacturing piezoelectric generator |
US20120206020A1 (en) * | 2011-02-15 | 2012-08-16 | Nihon Dempa Kogyo Co., Ltd. | Piezoelectric device |
CN107026632A (en) * | 2015-12-25 | 2017-08-08 | 日本电波工业株式会社 | Piezoelectric vibration piece and piezo-electric device |
US10673406B2 (en) * | 2016-10-28 | 2020-06-02 | Nihon Dempa Kogyo Co., Ltd. | Piezoelectric device |
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US7579762B2 (en) | 2009-08-25 |
JP5216210B2 (en) | 2013-06-19 |
JP2008166510A (en) | 2008-07-17 |
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